RSSB recommends prohibiting whistles

[Horizon22]

This seems like a fairly sensible strategy due to the hand-face contact it inevitably causes. It seems a few TOCs have already started doing this

https://www.rssb.co.uk/en/Insights-and-News/Coronavirus-pandemic-how-we-can-help-you

Advice on the use of whistles during the COVID-19 pandemic
We are advising that the use of whistles on platforms and stations (for example, as part of the train dispatch process), should cease for the duration of the COVID-19 pandemic to remove an infection risk to employees where safer alternatives can be used. Our advice is on a one-pager which you can download.

 

[philthetube]

I can think of two possible reasons for this, either it is to avoid hand to mouth contact or to avoid saliva spray as the whistle is blown.

I assume whistles are personal issue so no problem there.